By Leif Morten Tangen and Michael Lindqvist
The Norwegian Mapping Authority, Kartverket, became a full member of CRAF in June, 2023. The observatory, operated by Kartverket, is located at Brandal laguna in Ny-Ålesund, Svalbard. It is an internationally established fundamental geodetic VLBI station, which includes two 13.2 m telescopes inaugurated 2018, with receivers covering the band 2-14 GHz. Once fully operational, they will be part of the world’s first core sites within the Global Geodetic Observing System (GGOS), co-locating the four space geodetic techniques: Very Long Baseline Interferometry (VLBI), Satellite Laser Ranging (SLR), Global Navigation Satellite System (GNSS) and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS). As such, the observatory will be a fundamental part of a network of stations which define the global geodetic reference frame, and will be crucial to realise GGOS’s ambitious goals of 1 mm accuracy and 0.1 mm/yr stability.
The Observatory has a special protection in Norwegian law for RFI, “Fribruksforskriften“. It states in § 1. “Local area of operation” that “The regulation does not apply to the use of frequencies in the 2 GHz-32 GHz range in the geographical area within a radius of 20 km from the center of Ny-Ålesund. The regulation nevertheless applies to frequency use in this area for mandatory maritime and aeronautical safety-related equipment on board vessels and aircraft.”
In collaboration with SKAO’s lead spectrum manager Federico Di Vruno and ASTRON’s Cees Bassa, CRAF members conducted an observing campaign with the Dutch low-frequency radio telescope LOFAR. The aim was to measure, how much unintended electromagnetic radiation (UEMR) would be leaked from satellite onboard electronics and electrics.
The authors of the newly published paper were indeed successful, as they detected narrow- and broadband features associated with Starlink satellites. The intensity of the UEMR could be high enough to seriously disturb LOFAR measurements in the radio astronomy frequency band at 150 MHz, but further studies are required.
Further information can be found in various press releases, by the IAU CPS and the ESF.
Vehicle radars equipped in modern self-driving cars can no longer use the 24 GHz band and will be switching to the 76−81 GHz band. Radio Astronomy detections of molecules in the interstellar medium are performed in the band with several first-class radio telescopes in Europe such as the 30-m radio telescope (IRAM Pico Veleta, Spain), the NOEMA interferometer (IRAM Plateau de Bure, France), the Onsala 20 m radio telescope (OSO, Sweden) and the 40m radio telescope (IGN-Yebes Observatory, Spain) in the 76−81 GHz range.
To understand the future impact of the adoption of this band by cars for radio astronomy, CRAF proposed an aggregate study for 10 radiotelescopes: NOEMA (France), SRT (Italy), Yebes (Spain), Best (Hungary), Onsala (Sweden), Effelsberg (Germany) Noto (Italy), Metsähovi (Finland), IRAM (Spain), and Medicina (Italy). Studies were conducted by simulating the car distribution around the radio telescope according to road classification given by Open Street Map. Furthermore, the car density was varied with the aim of emulating traffic fluctuations between day and night and throughout the year. The results show variations between locations because of the high dependence on terrain attenuation around the site. Excluding Effelsberg located in a valley well shielded by mountains, the rest of the studied radio telescopes will require at least an exclusion zone of a radius of 10 km. This study was proposed to CEPT-ECC project team SE24 at the September 2022 meeting.